Remove undocumented and uncontrollable WiFI RSSI filter.

Commit d15e1b0 [1] in the 2.0.0 pull request espressif#4996 introduced a filter
to connect only to WiFi networks with a RSSI of -75 or better. This
results in strage behaviour, as a scan still shows networks, that can't
be connected to, even though with older versions, connecting to those
networks was possible and the connection (albeit slow) was stable.

Remove the RSSI filter for now by setting the threshold to -127, i.e.
the lowest possible value. Maybe in the future the filter threshold
could be exposed to users, to allow filtering out nearly unreachable
networks.

[1] github.com/espressif/pull/4996/commits/d15e1b0

Author: rtrbt

Diff for: libraries/WiFi/src/WiFiSTA.cpp

@@ -73,7 +73,7 @@ static void wifi_sta_config(wifi_config_t * wifi_config, const char * ssid=NULL,
     wifi_config->sta.listen_interval = listen_interval;
     wifi_config->sta.scan_method = scan_method;//WIFI_ALL_CHANNEL_SCAN or WIFI_FAST_SCAN
     wifi_config->sta.sort_method = sort_method;//WIFI_CONNECT_AP_BY_SIGNAL or WIFI_CONNECT_AP_BY_SECURITY
-    wifi_config->sta.threshold.rssi = -75;
+    wifi_config->sta.threshold.rssi = -127;
     wifi_config->sta.pmf_cfg.capable = true;
     wifi_config->sta.pmf_cfg.required = pmf_required;
     wifi_config->sta.bssid_set = 0;